IaC — Terraform

🌱 Seedling — core concepts documented, Hetzner and Azure patterns being added.

What Terraform Does

Terraform provisions infrastructure — servers, networks, databases, DNS records — from declarative configuration files (.tf).

It does NOT configure what's running on those servers (that's Ansible's job).

Terraform = "create a CX32 VPS on Hetzner with this SSH key and firewall"
Ansible   = "install Docker on that VPS and configure these services"

Core Concepts

Concept	Role
`main.tf`	Primary configuration file
Provider	Plugin for a specific platform (Hetzner, Azure, AWS)
Resource	A thing to create (server, network, volume)
State	Terraform's record of what it created (`terraform.tfstate`)
Module	Reusable, parameterised group of resources (DRY!)
`terraform.tfvars`	Variable values — keep secrets here, never commit to git

DRY via Modules

Instead of copy-pasting server resource blocks for dev/staging/prod:

# modules/hetzner-server/main.tf — defined once
resource "hcloud_server" "this" {
  name        = var.name
  server_type = var.server_type
  image       = "ubuntu-24.04"
  ssh_keys    = var.ssh_key_ids
}

# root main.tf — used multiple times, parameterised
module "vps_prod" {
  source      = "./modules/hetzner-server"
  name        = "eigen-prod"
  server_type = "cx32"
  ssh_key_ids = [hcloud_ssh_key.main.id]
}

Basic Workflow

terraform init      # download providers
terraform plan      # preview changes (always do this first)
terraform apply     # create/update infrastructure
terraform destroy   # tear down (careful in production)

Providers Used in eigenstack

Hetzner Cloud (hcloud) — VPS, volumes, firewalls, SSH keys
Cloudflare — DNS records, CNAME for subdomains
Azure (azurerm) — used in DevOps Azure EnterPrise LZ

Provider registry: registry.terraform.io

IaC — Ansible